1. Field of the Invention
The present invention relates to a variable valve control apparatus which includes a variable valve timing mechanism that adjusts actuation timing of a valve and a variable working angle mechanism that adjusts a working angle of the valve and includes variable valve control section that controls the variable valve timing mechanism or the variable working angle mechanism based on an engine load.
2. Description of the Related Art
The variable valve control apparatus described above includes variable valve control section in which a stable output is ensured at a wide range of engine revolution extending from a low range to a high range. In order to suppress surplus consumption of fuel in the low range, an intake side variable valve timing mechanism and an exhaust side variable valve timing mechanism actuated by an oil hydraulic mechanism are provided. And, a variable working angle mechanism for adjusting a lift amount of an intake valve is also provided. Then, according to an engine load, in the low range, retard angle control of the intake valve is performed by the intake side variable valve timing mechanism or control of decreasing the working angle is simultaneously performed by the variable working angle mechanism. And, in the high range, advance angle control of the intake valve is performed by the intake side variable valve timing mechanism or control of increasing the working angle is simultaneously performed by the variable working angle mechanism.
As shown in FIG. 11, the variable valve timing mechanism 99 includes a housing 92 for turning relatively to a cam shaft 90 including cams 90a for opening and closing an intake valve or an exhaust valve, a vane rotor 91 which is installed inside the housing 92 and rotates integrally with the cam shaft 90, plural vanes 94 installed in the outer circumference of the vane rotor 91, and an oil chamber 95 which is formed inside the housing 92 and receives the vanes 94 and guides an oil pressure. That is, it is configured so that the housing 92 rotates integrally with the vane rotor 91 and also the housing 92 turns relatively to the vane rotor 91.
The oil chamber 95 is partitioned by inner circumferential surfaces etc. of the housing 92, the vane rotor 91 and the vanes 94, and is configured to include a retard angle chamber 95a formed in a direction of opposite rotation of the cam shaft 90 with respect to the vanes 94 and an advance angle chamber 95b formed in a direction of rotation of the cam shaft 90 with respect to the vanes 94.
The retard angle chamber 95a and the advance angle chamber 95b are respectively provided with oil lines (not shown) for guiding hydraulic oil and it is configured so that by making the hydraulic oil act on the retard angle chamber 95a and the advance angle chamber 95b, a relative position of the vanes 94 to the oil chamber 95 is rotated and a phase of the cam shaft 90 is varied continuously.
That is, the variable valve timing mechanism 99 is configured so that when a rotation operation based on a rotation operation of a crankshaft (not shown) transferred through a timing belt 96 is performed by a cam pulley 97 formed in the outside of the housing 92, the housing 92 rotates integrally with the timing belt 96 and also a relative position of the vanes 94 to the oil chamber 95 is varied and thereby a phase between a rotational angle of the crankshaft and a rotational angle of the cam shaft 90 rotating integrally with the vanes 94 can be varied. That is, valve opening and closing timing of the intake valve or the exhaust valve with respect to an operation of a piston connected to the crankshaft can be varied. Further in other words, intake actuation timing of the intake valve or exhaust actuation timing of the exhaust valve can be varied.
As shown in FIGS. 12A and 12B, the variable working angle mechanism 89 is configured to include a control shaft 83, which is disposed between a roller rocker arm 81 connected to an intake valve 80 and an intake cam 82a disposed in an intake cam shaft 82 and is connected to an electric motor (not shown), an arm 84, which is formed on the control shaft 83 and receives the intake cam 82a, and a nose 85, which is formed on the control shaft 83 similarly and depresses the intake valve 80 through the roller rocker arm 81.
The intake cam 82a depresses the arm 84 with rotation driving of the intake cam shaft 82 and thereby the control shaft 83 rotates. And, the control shaft 83 rotates and thereby the roller rocker arm 81 is depressed by the nose 85 and the intake valve 80 is depressed. When the intake cam 82a is not in contact with the arm 84, that is, the arm 84 is not depressed by the intake cam 82a, the control shaft 83 rotates and returns to a predetermined angle by a return mechanism (not shown). Further, it is configured so that the predetermined angle can be varied by the electric motor.
That is, the variable working angle mechanism 89 is configured so that the amount of rotation of the control shaft 83 rotating by depression of the arm 84 by the intake cam 82a can be adjusted by varying the predetermined angle of the control shaft 83. And, the amount of rotation of the control shaft 83 can be adjusted and thereby a lift amount of the intake valve 80 through the roller rocker arm 81 by the nose 85 can be adjusted. In other words, it is configured so as to adjust a lift amount of the intake valve 80 by a working angle through the control shaft 83.
When timing at which both of the intake valve and the exhaust valve close at a same time after a piston of the cylinder passes an intake top dead center in the case where valve control is performed by the variable valve control section described above, there is fear that an inside of a cylinder becomes a negative pressure and oil is sucked up from an oil reservoir of the crank side and burns. In order to avoid occurring of the timing, such control is performed that preset a phase of the intake valve to the side of an advance angle than a target value based on simulation or experiment under different conditions.